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作 者 ：安慧;韦兰英;刘勇;上官周平

期 刊 ：植物营养与肥料学报 2007年 13卷 4期 页码：611-619

关键词：黄土高原；细根分布；白桦；油松；土壤养分；

Keywords:Loess Plateau, distribution characters of fine root, Pinus tabulaeformis forest, Betula platyphylla forest, soil nutrients,

摘 要 ：在黄土高原子午岭林区,对油松人工林、白桦天然林细根生物量、比根长、根长密度和细根表面积的垂直分布特征,以及这些根系指标与土壤水分、土壤容重、氮素和有机质的关系进行了研究。结果表明,油松人工林细根生物量随土壤深度增加呈单峰曲线,白桦林细根生物量随土壤深度增加呈减少趋势;油松林大部分根系生物量集中分布在0—40.cm土层中,其中0—20.cm土层占37%以上,20—40.cm集中了41%以上;表层土壤(0—20.cm)具有较高的比根长、根长密度和细根表面积,而底层(40—60.cm)的比根长、根长密度和细根表面积最低。油松林土壤全氮和有机质含量垂直变化趋势相似,随土壤深度的增加而降低;硝态氮(NO₃^--N)均随土壤深度的增加呈单峰曲线变化趋势,而铵态氮(NH4+-N)随土壤深度增加呈先降低后增加的抛物线趋势。白桦林75%的细根生物量集中在0—20.cm土层,比根长、根长密度和细根表面积的垂直分布规律与油松林相似,表层土壤白桦林细根表面积是油松人工林的3.91倍,而20—40.cm土层白桦林细根表面积比油松人工林降低了33%。白桦林土壤全氮、有机质含量、NO₃^--N和NH₄⁺-N垂直变化趋势与油松林相似。土壤水分、容重、全氮和有机质对油松和白桦细根分布的影响明显大于NH₄⁺-N和NO₃^--N。白桦林表层土壤有机质含量与细根生物量的相关性达到显著水平(r=0.99,P<0.05),白桦林表层土壤有机质含量与比根长和根长密度的相关性(分别为r=0.91,r=0.8)低于油松林(分别为r=0.95,r=0.94)。油松和白桦林0—40.cm土层细根表面积与土壤全氮相关性随土壤深度增加而下降,比根长和根长密度与土壤全氮相关性随土壤深度增加而增大。油松和白桦林20—60.cm土层细根生物量、细根表面积和根长密度随有机质含量的减少而增加,而比根长呈相反的变化规律。

Abstract:Fine root turnover plays an important role in below-ground carbon budget and affects the nutrient cycling in the terrestrial ecosystem.The vertical distribution characteristic of fine root biomass,specific root length(SRL),root lengthy density(RLD) and root surface area of artificial Pinus tabulaeformis and natural Betula platyphylla forests,and their relationship with soil moisture,bulk density,nitrogen and content of organic matter in Ziwuling of Loess Plateau were studied.The results indicated that vertical distribution of artifical Pinus tabulaeformis and natural Betula platyphylla forests showed different trends: fine root biomass of artifical Pinus tabulaeformis forests showed a single hump-shaped curve with soil depth increased,but fine root biomass of Betula platyphylla forests decreased with soil depth increased.Fine root biomass of Pinus tabulaeformis mostly distributed in the soil layer(040 cm),among which 37% of fine root biomass was distributed in the upper soil layer(0-20 cm),and 41% of fine root biomass was distributed in the soil layer(20-40 cm);root surface area,SRL and RLD of artificial Pinus tabulaeformis in the upper soil layer(0-20 cm) were greater than these in the lower two layers(20-40 cm,40-60 cm).Root surface area,SRL and RLD in the deep layer(40-60 cm) were the lowest compared to the upper two soil layers(0-20 cm and 20-40 cm).Total soil nitrogen and content of organic matter of Pinus tabulaeformis forests among different soil layer decreased with soil depths increased.Nitrate(NO₃^--N) showed a single hump-shaped curve with soil depth increased,but ammonia(NH₄⁺-N) showed a parabola curve,with lowest value found in 20-40 cm soil layer and highest value in 0-20 cm and 40-60 cm soil layer.75% of fine root biomass of Betula platyphylla was distributed in the upper soil layer(0-20 cm),vertical changes of root surface area,SRL and RLD of Betula platyphylla forests showed a similar trend regardless soil depths with artificial Pinus tabulaeformis forest.Root surface area of Betula platyphylla in upper soil depth(0-20 cm) was 3.91 times higher than that of artifical Pinus tabulaeformis,but root surface area of Betula platyphylla in the soil layer(20-40 cm) was 33% lower than that of artifical Pinus tabulaeformis.Vertical changes of total soil nitrogen,content of organic matter, NO₃^--N and NH₄⁺-N of Betula platyphylla among different layers presented a similar trend with artificial Pinus tabulaeformis forest.Distribution characteristics of fine root of artificial Pinus tabulaeformis and Betula platyphylla forests more significantly related to the changes of soil moisture,bulk density,total nitrogen and content of organic matter than ammonia(NH₄⁺-N) and nitrate(NO₃^--N).The fine root biomass was significantly correlated to the content of organic matter of Betula platyphylla forests in upper soil layer(020 cm).The correlation coefficient of root surface area of Pinus tabulaeformis and Betula platyphylla forests with total soil nitrogen decreased with the soil depth increased(0-40 cm),but the correlation coefficient of SRL and RLD with total soil nitrogen increased with the increasing of soil depth.Fine root biomass,root surface area and RLD increased with the decreasing content of organic matter in soil layer (20-60 cm),but SRL presented a reversed trend.

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